Biological Effects of Inhaled 239PuO2 in Beagles

Seven groups of 8–24 Beagle dogs, exposed to 239PuO2 aerosols by inhalation [mean initial lung depositions (ILD) of 0.0, 0.14, 0.63, 3.2, 13, 44 and 210 kBq] were observed throughout their lives to determine tissues at risk and dose-effect relationships. The mean average pulmonary retention half-time of 239Pu was 1,192 days. Most (70%) of the plutonium recovered at death in dogs surviving >10 years after exposure was found in the thoracic lymph nodes with ∼15% in lung, ∼10% in liver and ∼2% in bone. Eight dogs at the highest exposure levels died from radiation pneumonitis prior to a minimal 3-year latency period after exposure for the observation of lung tumors, with the first succumbing 337 days after exposure. Of 108 plutonium-exposed Beagles with ILD <100 kBq, 51 (47%) had lung tumors with significantly increased incidence in those dogs with total lung dose of ≥1.1 Gy at death. The primary non-neoplastic effects observed were lymphopenia, atrophy and fibrosis of the thoracic lymph nodes, radiation pneu...